<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>点击新增列</button>
    <ul>


    </ul>
</body>
<script>
    const addEm=document.createElement('li');
    const btn=document.querySelector('button');
    btn.addEventListener('click',function(evt){
        this.nextElementSibling.append(addEm);
        //btn.nextElementSibling.appendChild(addEm);
        addEm.innerText='这是新增列';
        evt.stopPropagation();
    });
</script>
</html>